Electrophotographic photosensitive member provided with a light receiving layer composed of a non-single crystal silicon material containing columnar structure regions and process for the production thereof

ABSTRACT

An electrophotographic photosensitive member comprising a substrate and a light receiving layer composed of a silicon-containing non-single crystal material disposed on said substrate, characterized in that said light receiving layer contains a plurality of columnar structure regions each grown from a nucleus situated in said light receiving layer wherein said plurality of columnar structure regions are arranged substantially in parallel to the thicknesswise direction of said light receiving layer and at a density in the range of 5/cm 2  to 500/cm 2 .

FIELD OF THE INVENTION

The present invention relates to an electrophotographic photosensitivemember comprising a substrate and a light receiving layer composed of anon-single crystal silicon material containing a plurality of columnarstructure regions therein which is disposed on said substrate, and aprocess for the production of said electrophotographic photosensitivemember.

RELATED BACKGROUND ART

The material of the photoconductive layer of an electrophotographicphotosensitive member is required to have a high sensitivity, high S/Nratio, absorption spectral characteristic matching the spectralcharacteristic of electromagnetic wave to be irradiated, rapid opticalresponsibility, and high dark resistance, to be excellent in mechanicaldurability, and to be not harmful to the human body at the time of use.

The public attention has been focused on the use of hydrogenatedamorphous silicon materials capable of satisfying the above requirementsin electrophotographic photosensitive members. Electrophotographicphotosensitive members having a photoconductive layer formed of suchhydrogenated amorphous silicon material are disclosed, for example, inJapanese Unexamined Patent Publication No. 86341/1979. Variouselectrophotographic photosensitive members having an amorphous siliconphotoconductive layer have been frequently used.

Japanese Unexamined Patent Publications Nos. 62254/1981 and 119356/1982disclose the use of hydrogenated amorphous silicon materials containingcarbon atoms in electrophotographic photosensitive members in order toimprove their electrophotographic characteristics.

Incidentally, the formation of a film of such amorphous silicon materialas above described as a constituent of the electrophotographicphotosensitive member can be conducted by the sputtering process,film-forming manner by decomposing raw material gas with the action ofthermal energy (that is, the so-called thermal-induced CVD process),film-forming manner by decomposing raw material gas with the action oflight energy (that is, the so-called light-induced CVD process), orfilm-forming manner by decomposing raw material gas with the action ofplasma (that is, the so-called plasma CVD process). Of thesefilm-forming processes, the plasma CVD process has been frequently used.And there are known various apparatus suitable for practicing the plasmaCVD process.

As the plasma CVD process, there is known the so-called microwave plasmaCVD process based on microwave glow discharge decomposition. Themicrowave plasma CVD process has been practiced on an industrial scale.

The microwave plasma CVD process is more advantageous in comparison withother film-forming processes in the viewpoints that a relatively higherdeposition rate and a relatively higher raw material gas utilizationefficiency are attained. U.S. Pat. No. 4,504,518 discloses a microwaveplasma CVD technique of making use of these advantages. The microwaveplasma CVD technique described in this patent literature is directed tothe formation of a high quality deposited film at a high deposition rateby practicing the microwave plasma CVD process at a reduced pressure of0.1 Tort or less.

Japanese Unexamined Patent Publication No. 186849/1985 discloses atechnique of improving the raw material gas utilization efficiency inthe microwave plasma CVD process. The technique described in thispublication is to improve the raw material gas utilization efficiency byarranging a substrate to circumscribe means for introducing microwaveenergy thereby forming an internal chamber (that is, a discharge space).Further, Japanese Unexamined Patent Publication No. 283116/1986discloses a technique of improving the property of a deposited filmformed by conducting the formation of the deposited film whilecontrolling ion bombardment to the film deposited by applying a desiredvoltage through a plasma potential-controlling electrode (that is, abias electrode) disposed in the discharge space.

U.S. Pat. No. 5,129,359 discloses a process for producing anelectrophotographic photosensitive member based on these microwaveplasma CVD techniques.

The process for producing an electrophotographic photosensitive memberdescribed in this U.S. Pat. No. 5,129,359 is practiced, for instance, byusing a film-forming apparatus shown in FIG. 6(A) as a longitudinalsection view and FIG. 6(B) as a cross section view.

In FIGS. 6(A) and 6(B), reference numeral 601 indicates a reactionchamber having a structure capable of being vacuum-sealed. Referencenumeral 602 indicates a microwave introducing dielectric window made ofa material (for example, quartz glass, alumina ceramics, or the like)which allows a microwave power to efficiently transmit into the reactionchamber 601 and can hermetically enclose the inside of the reactionchamber. Reference numeral 603 indicates a waveguide which serves totransmit a microwave power. The waveguide comprises a rectangularportion extending from a microwave power source (not shown) to theneighborhood of the reaction chamber and a cylindrical portion situatedin the reaction chamber.

The waveguide 603 is connected to the microwave power source (not shown)through a stub tuner (not shown) and an isolator (not shown). Referencenumeral 604 indicates an exhaust pipe. The exhaust pipe is open into thereaction chamber 601 through one end thereof and is connected to anexhaust device (not shown) through the remaining end thereof. Referencenumeral 606 indicates a discharge space circumscribed by a plurality ofsubstrates 605. Reference numeral 611 indicates a D.C. power source (abias power source) which serves to apply a D.C. voltage to a biaselectrode 612.

The process for producing an electrophotographic photosensitive memberusing the film-forming apparatus of the above-described constitution isconducted, for example, in the following manner. That is, the reactionchamber 601 is evacuated through the exhaust pipe 604 by operating avacuum pump (not shown) to bring the inside of the reaction chamber 601to a vacuum of 1×10⁻⁷ or less. The substrates 605 are then heated to andmaintained at a temperature of 200° to 300° C. by means of heaters 607.Thereafter, raw material gases such as silane gas, hydrogen gas, and thelike are introduced into the reaction chamber 601 through gas feed means(not shown). Then, a microwave power of 2.45 GHz from the microwavepower source is introduced into the reaction chamber 601 through thewaveguide 603 and the dielectric window 602. Simultaneously with this,the bias power source 611 electrically connected to the bias electrode612 positioned in the discharge space 606 is switched on to apply adesired bias voltage between the bias electrode 612 and the substrates605. In this case, the raw material gases in the discharge space 606circumscribed by the substrates are excited and decomposed with theaction of an energy of the microwave power, wherein ion bombardment isdirected onto the substrates 605 by virtue of an electric fieldgenerated between the bias electrode 611 and the substrates 605, wherebya deposited film is formed on each of the substrates 605. During thisfilm formation, each of the substrates 605 is rotated by revolving therotary shaft 609 by means of a motor 610.

According to this process, it is possible to obtain electrophotographicphotosensitive members having practically acceptable electrophotographiccharacteristics and which are satisfactory in terms of uniformity at arelatively low production cost. However, as for the electrophotographicphotosensitive members produced by the conventional process, there arestill remained problems which are required to be resolved. For instance,upon film formation by the conventional process, in the zone in whichfilm formation is carried out at a relatively higher film-forming speed,it is difficult to stably obtain a deposited film which is homogeneousin terms of film quality, satisfies the requirements for optical andelectric characteristics desired therefor, and is free of defectsresulting in providing defective images upon image formation by theelectrophotographic image forming process, at a high yield.

Specifically, as for the deposited film obtained in this case, it isoften accompanied by a defect which leads to occurrence of unevendensity for an image reproduced. The occurrence of uneven density for animage reproduced is not so problematic in the case of reproducing anoriginal containing characters only. However, it is apparentlyproblematic in the case of reproducing a halftone original such as aphotograph, especially when the reproduction thereof is conducted at ahigh image-forming process speed. Further in the case of reproduction ofa colored image for which demand has increased in recent years, it isrequired for an image reproduced to be precisely uniform in terms of theimage density. In this case, the above occurrence of uneven density is aserious problem.

In addition, the electrophotographic photosensitive member comprisingsuch deposited film does not satisfactorily comply with a demand inrecent years for an improvement in the resolution for an imagereproduced. The resolution of an image reproduced is governed by notonly the electrophotographic photosensitive member but also theelectrophotographic image-forming process including development andfixing steps which is employed upon the image formation. In recentyears, a fine particle toner has been developed, and theelectrophotographic image-forming process has been improved so as tomake full advantage of such fine particle toner. Along with this, thereis an increased demand for the electrophotographic photosensitive memberto be improved so that an improvement is attained for the resolution foran image reproduced. However, making an electrophotographicphotosensitive member comprising the above deposited film is difficult,to satisfy this demand.

European Patent Publication No. 454456 A1 proposes a technique ofeliminating the above problems. Particularly, this patent publicationdiscloses a light receiving member having a photoconductive layercomposed of a non-single crystal silicon carbide containing fluorineatoms in a trace amount of 1 to 95 atomic ppm and oxygen atoms in acontrolled amount in which the photoconductive layer is effectivelyrelaxed in terms of internal distortion and is free of spherical growthdefects at the surface and which is capable of preventing occurrence of"minute blank area", occurrence of "coarseness" and occurrence of"ghost" on an image reproduced. The technique described in this patentpublication is aimed at diminishing the spherical growth defect at thesurface of the light receiving layer of the light receiving member so asto stabilize and improve the quality of an image reproduced.

However, it is almost impossible to completely eliminate the appearanceof such spherical growth defect at the surface of a photoconductivelayer composed of a non-single crystal silicon carbide even byincorporating a prescribed amount of fluorine atoms and oxygen atomsthereinto. In fact, the present inventors prepared a light receivingmember of the above constitution and subjected the light receivingmember to continuous reproduction of a halftone original at animage-forming speed of 50 sheets per minute over a long period of time.As a result, there were found occurrence of uneven density andoccurrence of a reduction in the resolution for the images reproducedafter repetition of the copying shots. The causes for these problems areconsidered due to the spherical growth defect present at the surface ofthe photoconductive layer.

Japanese Unexamined Patent Publications Nos. 84965/1987 and 188665/1987disclose a technique of eliminating the problems of anelectrophotographic photosensitive member due to unevenness in thethickness thereof by grinding the surface of the electrophotographicphotosensitive member. However, these patent publications do notdescribe anything about the interrelations between the surface grindingand the defects occurred on an image reproduced.

Incidentally, the present inventors found that the surface grindingtechnique described in these patent publications is not satisfactorilyeffective in making the electrophotographic photosensitive member suchthat it stably provides a high quality reproduced image excelling inresolution and density uniformity upon high speed image reproduction.

In order to stably obtain a high quality reproduced image excelling inresolution and density in high speed image reproduction, due care shouldbe made so that no problem is occurred due to reflection of light usedfor the exposure. For instance, in the case of conducting imagereproduction using an amorphous silicon series photosensitive member asthe photoreceptor in the digital copying machine in which asemiconductor laser is used as the exposure light source, there is usedas the semiconductor laser a near infrared laser having an energy whichis lower than the energy band gap of the amorphous silicon film of thephotosensitive member, wherein the laser rays are not completelyabsorbed by the amorphous silicon film and the residual laser rays otherthan those absorbed by the amorphous silicon film are transmitted orreflected. In this case, the laser rays reflected at the surface of thephotosensitive member often interfere with the laser rays reflected atthe interface between the amorphous silicon film and the substrate orthe layer interface of the amorphous silicon film to provide aninterference fringe pattern on an image reproduced.

U.S. Pat. No. 4,808,504 discloses a technique of eliminating the problemof providing such interference fringe pattern on an image reproduced.Particularly, this patent literature describes an electrophotographicphotosensitive member comprising a substrate having an uneven-shapedsurface composed of a plurality of spherical dimples and a lightreceiving layer disposed on said uneven-shaped surface of the substratein which interference fringes occurred are dispersed within thespherical dimples to prevent images reproduced from being accompanied byinterference fringe patterns.

This electrophotographic photosensitive member has been evaluated asbeing effective to prevent the occurrence of an interference fringepattern on an image reproduced. However, the electrophotographicphotosensitive member is disadvantageous in the viewpoint that theproduction cost thereof unavoidably becomes remarkable because specificfacility and process are required for forming the uneven-shaped surfacecomposed of a plurality of spherical dimples at the surface of asubstrate in the preparation of the electrophotographic photosensitivemember.

SUMMARY OF THE INVENTION

The present invention is aimed at providing an improvedelectrophotographic photosensitive member which is free of the foregoingproblems relating to occurrence of uneven density and reduction inresolution on an image reproduced which are found in the case of theconventional electrophotographic photosensitive member.

Another object of the present invention is to provide anelectrophotographic photosensitive member comprising a substrate and alight receiving layer composed of a non-single crystal materialcontaining silicon atoms as a matrix disposed on said substrate,characterized in that said light receiving layer contains a plurality ofcolumnar structure regions each grown based on a nucleus present in saidlight receiving layer which are spacedly arranged substantially inparallel to the thicknesswise direction of said light receiving layer ata density of 5/cm² to 500/cm².

A further object of the present invention is to a process which enablesone to produce the above electrophotographic photosensitive member bythe microwave plasma CVD process at a reduced production cost.

In order to solve the foregoing problems in the conventionalelectrophotographic photosensitive member and to attain the aboveobjects, the present inventors made extensive studies by preparing anumber of electrophotographic photosensitive members each having a lightreceiving layer composed of a non-single crystal silicon material(specifically, an amorphous silicon material) containing a plurality ofcolumnar structure regions intentionally formed therein. As a result,the present inventors obtained the following findings. That is, (1) whenthe light receiving layer formed on a substrate is comprised of anon-single crystal silicon material containing a plurality of columnarstructure regions established substantially in parallel to thethicknesswise direction, the resulting photosensitive member becomessuch that no charge flow occurs in the thicknesswise direction of thelight receiving layer and because of this, an improvement is attained interms of the resolution of an image reproduced; and (2) the reflectionof incident light at the surface of the photosensitive member, that atthe layer interface and that at the surface of the substrate aredispersed to diminish the occurrence of unevenness in terms of lightreflection (that is, to diminish a difference in terms of the absorbedamount of light).

The present invention has been accomplished based on these findings. Thepresent invention is of the gist which will be described in thefollowing. That is, the present invention is directed to an improvementin an electrophotographic photosensitive member comprising a substrateand a light receiving layer composed of a non-single crystal materialcontaining silicon atoms as a matrix disposed on said substrate, theimprovement is characterized in that said light receiving layer containsa plurality of columnar structure regions each grown based on a nucleuspresent in said light receiving layer which are arranged substantiallyin parallel to the thicknesswise direction of said light receiving layerat a density of 5/cm² to 500/cm².

The present invention includes a process for producing the aboveelectrophotographic photosensitive member. Particularly, the processaccording to the present invention is for producing anelectrophotographic photosensitive member by introducing a gaseoussilicon atom-containing raw material into a substantially enclosedreaction chamber having a discharge space, and supplying a microwaveenergy into the reaction chamber to generate a plasma in the dischargespace to thereby form a film composed of a silicon-containing non-singlecrystal material as a light receiving layer on a substrate positioned inthe reaction chamber, characterized by comprising the steps of:

(i) forming a film as a partial layer region of said light receivinglayer,

(ii) spacedly depositing a plurality of nucleuses, each capable of beinga nucleus for growing a columnar structure region based on said nucleus,on said partial layer region respectively in an immobilized state, and

(iii) repeating the film-forming step (i) to form a film on the surfaceof the above film having said plurality of nucleuses deposited thereonwhile growing a columnar structure region based on each of saidplurality of nucleuses whereby a plurality of columnar structure regionsare formed substantially in parallel in the thicknesswise direction at adensity of 5/cm² to 500/cm².

The electrophotographic photosensitive member having the specific lightreceiving layer composed of a non-single crystal silicon material andcontaining a plurality of columnar structure regions being arrangedsubstantially in parallel to the thicknesswise direction at a specificdensity according to the present invention is markedly advantageous inthat the columnar structure regions function to prevent charges fromflowing in the direction perpendicular to the thicknesswise direction ofthe light receiving layer composed of the non-single crystal siliconmaterial and because of this, no smudging is occurred for an imagereproduced and an improvement is attained in the resolution of saidimage reproduced, and in addition to this, the reflection of incidentlight at the surface of the electrophotographic photosensitive member,that at the layer interface, and that at the surface of the substrateare dispersed to diminish the occurrence of unevenness in terms of lightreflection (that is, to diminish a difference in terms of the absorbedamount of light), resulting in making an image reproduced to be uniformin density as desired.

The process for producing an electrophotographic photosensitive memberaccording to the present invention makes it possible to produce theabove-described, improved electrophotographic photosensitive member at ahigh yield and at a low production cost.

The present inventors made studies of the reasons why the conventionalelectrophotographic photosensitive member is not satisfactory in termsof the density uniformity for an image reproduced, while focusingattention on the configuration thereof which usually comprises as asubstrate and a multi-layered structure disposed on said substrate,comprising a plurality of layers each having a different function suchas a charge generation layer, charge transportation layer, surfaceprotective layer, charge injection inhibition layer, and the like. As aresult, there were obtained findings as will be described in thefollowing. That is, the layers stacked are more or less different fromeach other in terms of the reflective index and because of this,reflection of incident light occurs at each of the interfaces among thelayers stacked, in addition, incident light is also reflected not onlyat the surface of the photosensitive member but also at the surface ofthe substrate, wherein those lights reflected interfere to strengthen orweaken with each other because they are different from each other interms of optical path length. In this case, if the stacked structureshould have a layered portion comprising a plurality of layers having anidentical property, they are different from each other in terms of thethickness and incident angle of light, and because of this, the opticalpath length of incident light is different depending upon the positionof the photosensitive member involved. This situation causes anunevenness in light reflection, which leads to providing an unevennessin terms of the density for an image reproduced.

In addition to the above, the present inventors made studies of thereasons why the conventional electrophotographic photosensitive memberis not satisfactory in terms of the resolution for an image reproduced.As a result, there were obtained findings that in theelectrophotographic image-forming process using the photosensitivemember, charges are retained at the surface of the substrate and that ofthe light receiving layer by way of the corona discharging and chargespresent in a given region of the photosensitive member subjected toexposure are extinguished, wherein an electric field generated by thecharges remained in non-exposed region of the photosensitive membermakes some of the charges generated in the light receiving layer uponexposure to flow in the crosswise direction (that is, the directionperpendicular to the thicknesswise direction of the light receivinglayer), resulting in causing a deterioration in the resolution of animage reproduced.

The present inventors made extensive studies in order to eliminate theabove problems relating to the occurrence of uneven density and theoccurrence of deterioration in the resolution for an image reproduced inthe conventional electrophotographic photosensitive member. As a result,the present inventors obtained a knowledge that these problems could besolved by establishing a plurality of columnar structure regions in alight layer composed of a non-single crystal material as the lightreceiving layer disposed on the substrate such that they are spacedlyarranged substantially in parallel to the thicknesswise direction of thelayer.

In order to confirm whether or not this knowledge is practical, thepresent inventors conducted the following experiments.

EXPERIMENT 1

In this experiment, there were prepared a plurality of photosensitivemember samples in a manner of scattering Si-powder as a nucleus forgrowing the foregoing columnar structure region on the surface of an Alsubstrate and forming a deposited film as a light receiving layer on thesurface of the Al substrate. As for each of the photosensitive membersamples, the deposited film as the light receiving layer was examined bythe SEM. In addition, each of the photosensitive member samples wassubjected to the electrophotographic image-forming process to examineits electrophotographic characteristics.

As the film-forming apparatus, there was used a fabrication apparatus ofthe constitution shown in FIGS. 2(A) and 2(B). The apparatus shown inFIGS. 2(A) and 2(B) is of the same constitution as the apparatus shownin FIGS. 6(A) and 6(B) except for the following points. That is, theformer apparatus is additionally provided with supply ports 213 forsupplying nucleuses for growing columnar structure regions and amechanism for revolving the substrates 205 in addition to the mechanismfor rotating each of them, which are not disposed in the apparatus shownin FIGS. 6(A) and 6(B).

Particularly, in FIGS. 2(A) and 2(B), reference numeral 201 indicates areaction chamber, reference numeral 202 indicates a microwaveintroducing dielectric window made of an alumina ceramic which allows amicrowave power to efficiently transmit into the reaction chamber 201and can hermetically enclose the inside of the reaction chamber, andreference numeral 203 indicates a waveguide which serves to transmit amicrowave power. The waveguide 203 is connected to a microwave powersource (not shown) through a stub tuner (not shown) and an isolator (notshown). Reference numeral 204 indicates an exhaust pipe which is openinto the reaction chamber 201 through one end thereof and is connectedto an exhaust device (not shown) through the remaining end thereof.Reference numeral 206 indicates a discharge space circumscribed by aplurality of substrates 205. Reference numeral 211 indicates a D.C.power source (a bias power source) which serves to apply a D.C. voltageto a bias electrode 212. Reference numeral 214 indicates a sealingmember, and reference numeral 216 indicates a revolution plate.Reference numeral 215 indicates a motor for rotating the revolutionplate 216.

The formation of the light receiving layer was conducted as follows. Thereaction chamber 201 containing a plurality of Al substrates 205 eachbeing supported on a rotary shaft was evacuated through the exhaust pipe204 to bring the inside to a vacuum of 1×10⁻⁷ Torr. Then, the substrates205 were heated to and maintained at a temperature of 250° C. by meansof heaters 207. The substrates 205 were rotated by means of the motor210 while revolving them by means of the motor 215. Herein, Si powder of10 μm in mean particle size was supplied together with Ar gas into thereaction chamber 201 through the supply ports 213 for 2 minutes, underconditions of 2×10⁴ Pa for the spouting pressure of the Si powder and1000 sccm for the flow rate of the Ar gas, whereby the Si powder wasspread over the surface of each substrate. Thereafter, SiH₄ gas, He gas,CH₄ gas, and SiF₄ gas were introduced into the reaction chamber 201through gas feed means (not shown) at respective flow rates of 350 sccm,100 sccm, 50 sccm, and 1 sccm. Successively, the gas pressure in thereaction chamber 201 was adjusted to and maintained at 4.0 mTorr. Themicrowave power source was then switched on to apply a microwave energyof 2.45 GHz in frequency and 1000 W in power into the reaction chamber201. Simultaneously with this, a bias voltage of 70 V was appliedthrough the bias electrode 212. By this, the raw material gases wereexcited and decomposed with the action of the microwave energy in thedischarge space 206 to produce a plasma while causing ion bombardment byvirtue of an electric field generated between the bias electrode 212 andthe substrate 205, whereby an amorphous silicon carbide film containinghydrogen and fluorine atoms (a-SiC:H:F film) as the light receivinglayer was formed on each of the substrates 205 at a thickness of 20 μm.Thus, there were obtained a plurality of photosensitive member samples.As for each of the resultant amorphous silicon carbide films each formedon the Al substrate 205, a part of which was cut to obtain a specimenfor SEM examination, and the specimen was examined by means of the SEM.As a result, there were observed a plurality of cracks extending fromthe Si crystal nucleuses to the surface of the light receiving layer anda plurality of protrusions formed at the surface. In view of this, thelight receiving layer of each of the photosensitive member samples wasfound to be inferior in terms of the quality.

In order to remove the protrusions at the surface of the light receivinglayer, each photosensitive member sample was subjected to surfacetreatment by a polishing apparatus of the constitution shown in FIG. 3.The polishing apparatus shown in FIG. 3 is for grinding the surface ofan object by fixing the object on the rotary shaft and rotating therotary shaft while pressure contacting an abrasive tape to the surfaceof the photosensitive member on the rotary shaft.

The surface treatment of the photosensitive member by the polishingapparatus was conducted in the following manner. That is, a polishingunit 302 in the polishing apparatus body 301 was lifted upward and itwas secured by a clamp 303. Then, the photosensitive member sample 305was assembled with a supporting table 304 and the assembly was fixed toa rotary shaft 306. The clamp 303 was then loosed to lower the polishingunit 302, whereby an abrasive tape 308 was press-contacted with thesurface of the photosensitive member sample 305 by means of a pressureroller 307. Herein, a polyester film applied with silicon carbide powderof 8 μm in mean particle size to the surface thereof was used as theabrasive tape 308, and as the pressure roller 307, there was used onehaving a coat composed of a urethane rubber of 80 in the JIS hardness.

In the above, the conditions upon press-contacting the abrasive tape 308with the surface of the photosensitive member sample 305 through thepressure roller were made to be 40 g/cm in terms of linear load and 0.5mm in contact width (nip width in other words) by regulating a pressurecontacting spring 309. The surface treatment was conducted by actuatingvariable speed motors 310 and 311 for 5 minutes, wherein the abrasivetape 308 was moved at a feed speed of 10 mm/min., and the photosensitivemember sample 305 was rotated at a rotation speed of 300 mm/sec.

In this way, the surface of each photosensitive member sample wastreated. Each of the photosensitive member samples thus treated was setto a modification of the copying machine NP 9330 produced by CANONKabushiki Kaisha for experimental purposes, in which image formation wasconducted to reproduce a character original in order to evaluate theelectrophotographic characteristics of the photosensitive member sample.As a result, as for each of the photosensitive members dedicated for theevaluation, it was found that images reproduced at the initial stageseem acceptable in terms of the image quality but thereafter, as theimage formation is repeated, the quality of an image reproduced becomesexacerbated, wherein there is provided such an image that the charactersreproduced are hardly recognized.

The reason why any of the photosensitive member samples is poor inelectrophotographic characteristics is considered to be due to thecracks in the deposited film as the light receiving layer which occurredas a result of the deposited film having been formed on the Si crystalnucleuses unstably deposited on the Al substrate.

EXPERIMENT 2

In this experiment, taking the results obtained in Experiment 1 intoconsideration, the spread of the Si fine particles as the columnarstructure region growing nucleuses onto the Al substrates was conductedafter a deposited film had been formed on each of the substrates at acertain thickness. That is, the procedures of Experiment 1 wererepeated, except that the step of spreading the Si fine particles ontoeach of the Al substrates was conducted after a deposited film had beenformed on each of the substrates at a certain thickness.

Particularly, there were prepared a plurality of photosensitive membersamples in the following manner. The reaction chamber 201 was evacuatedto bring the inside to a desired vacuum. Then, the Al substrates 205were heated to and maintained at a temperature of 250° C. The substrates205 were rotated while revolving them. SiH₄ gas, He gas, CH₄ gas, andSiF₄ gas were then introduced into the reaction chamber 201 atrespective flow rates of 350 sccm, 100 sccm, 50 sccm, and 1 sccm.Successively, the gas pressure in the reaction chamber 201 was adjustedto and maintained at 4.0 mTorr. The microwave power source was thenswitched on to apply a microwave energy of 2.45 GHz in frequency and1000 W in power into the reaction chamber 201. Simultaneously with this,a bias voltage of 70 V was applied through the bias electrode 212. Bythis, an amorphous silicon carbide film containing hydrogen and fluorineatoms (a-SiC:H:F film) as the light receiving layer was formed on eachof the substrates 205 at a thickness of 5 μm. Thereafter, the microwavepower source and the bias power source were switched off and theintroduction of the raw material gases was suspended. Then, Si powder of10 μm in mean particle size was supplied together with Ar gas into thereaction chamber 201 through the supply ports 213 for 2 minutes, underconditions of 2×10⁴ Pa for the spouting pressure of the Si powder and1000 sccm for the flow rate of the Ar gas, whereby the Si powder wasspread on the surface of the 5 μm thick amorphous silicon carbide film(the a-SiC:H:F film) formed on each of the substrates. Successively, theabove film-forming procedures of introducing the raw material gases intothe reaction chamber 201 and applying the microwave energy into thereaction chamber while applying the bias voltage through the biaselectrode 212 were repeated to thereby stack a 15 μm thick amorphoussilicon carbide film (a-SiC:H:F film).

Thus, there were obtained a plurality of photosensitive member samples.Each of the resultant amorphous silicon carbide films each formed on thesubstrate was examined by the SEM in the same manner as in Experiment 1.As a result, there were observed a plurality of columnar regions grownfrom the Si crystal nucleuses spread on the initially formed 5 μm thickamorphous silicon carbide film (the a-SiC:H:F film) apparently inparallel to the thicknesswise direction. In this case, there wereobserved some Si crystal nucleuses from which no columnar region havingbeen grown.

Each photosensitive member sample was subjected to surface treatment bythe polishing apparatus shown in FIG. 3 in the same manner as inExperiment 1. Each of the photosensitive member samples thus treated wassubjected to image formation in the same manner as in Experiment 1, inorder to evaluate the electrophotographic characteristics of thephotosensitive member sample. As a result, it was found that each of thephotosensitive member samples reproduces images which are markedlysurpassing those reproduced by the photosensitive member samplesobtained in Experiment 1. However, as for each of the photosensitivemembers dedicated for the evaluation, it was found that imagesreproduced after about 50,000 times image-forming shots aredistinguishably inferior in terms of the image quality (specifically,deterioration in the resolution and occurrence of white spots). In orderto ascertain the reason for this, as for each of the photosensitivemembers having been subjected to the repetitive image-forming shots ofmore than 50,000 times, a part of the deposited film as the lightreceiving layer formed on the Al substrate was cut to obtain a specimenfor SEM examination, and the specimen was examined by means of the SEM.As a result, there were observed a plurality of columnar regions grownfrom the Si crystal nucleuses spread on the initially formed 5 μm thickamorphous silicon carbide film (the a-SiC:H:F film) and which arearranged apparently in parallel to the thicknesswise direction and inaddition to these columnar regions, a plurality of coarse regions eachcomprising a Si crystal nucleus with no deposited film. It is consideredthat these coarse regions would entail the deterioration in theresolution and occurrence of white spots for the images reproduced. Assuch coarse regions occurred in the deposited film as the lightreceiving layer, it is considered that they would have been occurred dueto those Si crystal nucleuses insufficiently immobilized on theinitially formed amorphous silicon carbide film.

EXPERIMENT 3

In this experiment, in order for Si-powder to be spread such that Sicrystal nucleuses are deposited on the surface of an amorphous siliconcarbide film (that is, an a-SiC:H:F film), which is initially formed,respectively in an immobilized state, the Si-powder was electricallycharged and it was spread over the surface of the amorphous siliconcarbide film (the a-SiC:H:F film) formed on each substrate so that theSi crystal nucleuses were deposited on the amorphous silicon carbidefilm by virtue of an electric field generated between the Si-powder andsubstrate. The film formation in this experiment was conducted by usinga modification of the film-forming apparatus shown in FIGS. 2(A) and2(B), which is additionally provided with a charger comprising atungsten wire of 0.5 mm in diameter disposed at each of the supply ports213, a mechanism of applying a D.C. voltage to the charger so as tocause corona discharge thereby charging the Si-powder upon supplying itinto the reaction chamber, and a mechanism for applying a D.C. biasvoltage to the substrates 205.

In this experiment, the procedures of Experiment 2 were repeated, exceptthat the step of spreading the Si-powder on each substrate was conductedwhile charging the Si-powder, applying a D.C. bias voltage to each Alsubstrate 205, and utilizing an electric field between the Si-powder andsubstrate.

Particularly, there were prepared a plurality of photosensitive membersamples in the following manner. The reaction chamber 201 was evacuatedto bring the inside to a desired vacuum. Then, the Al substrates 205were heated to and maintained at a temperature of 250° C. The substrates205 were rotated while revolving them. SiH₄ gas, He gas, CH₄ gas, andSiF₄ gas were then introduced into the reaction chamber 201 atrespective flow rates of 350 sccm, 100 sccm, 50 sccm, and 1 sccm.Successively, the gas pressure in the reaction chamber 201 was adjustedto and maintained at 4.0 mTorr. The microwave power source was thenswitched on to apply a microwave energy of 2.45 GHz in frequency and1000 W in power into the reaction chamber 201. Simultaneously with this,a bias voltage of 70 V was applied through the bias electrode 212. Bythis, an amorphous silicon carbide film containing hydrogen and fluorineatoms (a-SiC:H:F film) as the light receiving layer was formed on eachof the substrates 205 at a thickness of 5 μm. Thereafter, the microwavepower source and the bias power source were switched off and theintroduction of the raw material gases was suspended. Then, whileapplying a D.C. voltage of 5 kV to the charger disposed at each of thesupply port 213 to cause corona discharge whereby charging Si-powder andapplying a D.C. voltage of -100 V to each of the Al substrates, theSi-powder was supplied together with Ar gas into the reaction chamber201 through the supply ports 213 for 2 minutes under conditions of 2×10⁴Pa for the spouting pressure of the Si-powder and 1000 sccm for the flowrate of the Ar gas, whereby the Si powder was spreaded on the surface ofthe amorphous silicon carbide film formed on each of the substrates.Thereafter, the application of the D.C. voltage to the Al substrates wasterminated. Successively, the above film-forming procedures ofintroducing the raw material gases into the reaction chamber andapplying the microwave energy into the reaction chamber while applyingthe bias voltage through the bias electrode 212 were repeated to therebystack a 15 μm thick amorphous silicon carbide film (a-SiC:H:F film).

Thus, there were obtained a plurality of photosensitive member samples.Each of the resultant amorphous silicon carbide films individuallyformed on the substrate was examined by the SEM as well as in Experiment2. As a result, there were observed a plurality of columnar regionsgrown from all the Si crystal nucleuses spread on the initially formed 5μm thick amorphous silicon carbide film (the a-SiC:H:F film) apparentlyin parallel to the thicknesswise direction.

Each photosensitive member sample was subjected to surface treatment bythe polishing apparatus shown in FIG. 3 as well as in Experiment 2. Eachof the photosensitive member samples thus treated was subjected to imageformation as well as in Experiment 2, in order to evaluate theelectrophotographic characteristics of the photosensitive member sample.As a result, it was found that each of the photosensitive member samplesreproduces images which are surpassing those reproduced by thephotosensitive member samples obtained in Experiment 2, wherein imagesreproduced after 100,000 image-forming shots excel in quality withoutbeing accompanied by such defects that were found in the aboveexperiment. As for the reason why each of the photosensitive membersamples provides high quality reproduced images even after havingrepeated the image formation over a long period of time, it isconsidered such that the Si crystal nucleuses from the Si-powder weredeposited on the initially formed amorphous film in immobilized stateupon spreading the Si-powder and a plurality of columnar structureregions were grown from all the Si crystal nucleuses such that they arearranged apparently in parallel to the thicknesswise direction.

EXPERIMENT 4

In this experiment, based on the results obtained in Experiment 3,studies were made in order to find out a desirable range for the densityof the columnar structure regions formed in the deposited film as thelight receiving layer.

In this experiment, there were prepared a variety of photosensitivemembers of the configuration shown in FIG. 1(A). In FIG. 1(A), referencenumeral 102 indicates a substrate, and reference numeral 104 indicates alayer which functions as a photoconductive layer, wherein the layer iscomposed of a non-single crystal material (an amorphous material,microcrystalline material or polycrystalline material) containingsilicon atoms as a matrix. Reference numeral 103 indicates a chargeinjection inhibition layer, and reference numeral 105 indicates asurface layer. Reference numeral 110 indicates a columnar structureregion, and reference numeral 111 indicates a crystal nucleus for thecolumnar structure region.

For each photosensitive member, there were prepared a plurality ofphotosensitive member samples using the film-forming apparatus used inExperiment 3 as will be described below.

That is, the reaction chamber 201 was evacuated to bring the inside to adesired vacuum. Then, the Al substrates 205 were heated to andmaintained at a temperature of 250° C. The substrates 205 were rotatedwhile revolving them. SiH₄ gas, He gas, B₂ H₆ gas, and NO gas were thenintroduced into the reaction chamber 201 at respective flow rates of 350sccm, 100 sccm, 1000 ppm, and 10 sccm. The gas pressure in the reactionchamber 201 was adjusted to and maintained at 4.0 mTorr. The microwavepower source was then switched on to apply a microwave energy of 2.45GHz in frequency and 1000 W in power into the reaction chamber 201.Simultaneously with this, a bias voltage of 70 V was applied through thebias electrode 212. By this, a 3 μm thick a-Si:H:N:B film as the chargeinjection inhibition layer 103 on each of the Al substrates 205. Then,the introduction of the B₂ H₆ gas and NO gas was terminated, and whilecontinuing the introduction of the SiH₄ gas and He gas into the reactionchamber 201, CH₄ gas and SiF₄ were additionally introduced into thereaction chamber at respective flow rates of 50 sccm and 1 sccm, tothereby form a 5 μm thick a-SiC:H:F film on the above film. Thereafter,the microwave power source (not shown) and the bias power source wereswitched off and the introduction of the raw material gases wassuspended. Then, while applying a D.C. voltage of 5 kV to the chargerdisposed at each of the supply port 213 to cause corona dischargewhereby charging Si-powder and applying a D.C. voltage of -100 V to eachof the Al substrates, the Si-powder was supplied together with Ar gasinto the reaction chamber 201 through the supply ports 213 for a givenperiod of time in the range of 10 seconds to 5 minutes under conditionsof 2×10⁴ Pa for the spouting pressure of the Si-powder and 800 sccm forthe flow rate of the Ar gas, whereby the Si powder was spreaded on thesurface of the amorphous silicon carbide film formed on each of thesubstrates 205. Thereafter, the application of the D.C. voltage to theAl substrates was terminated. Then, the above film-forming procedures ofintroducing the raw material gases into the reaction chamber andapplying the microwave energy into the reaction chamber while applyingthe bias voltage through the bias electrode 212 were repeated to therebystack a 15 μm thick a-SiC:H:F film, whereby a photoconductive layer 104was formed. On the photoconductive layer on each of the substrates, a0.5 μm thick a-SiC:H film as the surface layer 105 under thefilm-forming conditions shown in Table 1. The film-forming conditionsemployed for the formation of the layers 103, 104 and 105 arecollectively shown in Table 1. Thus, there were obtained a variety ofphotosensitive members which are different with respect to the period oftime during which the Si-powder was supplied.

Each of the photosensitive members obtained was subjected to surfacetreatment by the polishing apparatus shown in FIG. 3 as well as inExperiment 2.

The photosensitive member thus treated was set to the modification ofthe copying machine NP 9330 produced by CANON Kabushiki Kaisha forexperimental purposes, wherein image formation was conducted using agiven test chart to reproduce images. Based on the images reproduced,evaluation was conducted with respect to the electrophotographiccharacteristics. The evaluated results obtained are collectively shownin Table 2. The evaluation of each of the evaluation items shown inTable 2 was conducted in the manner as will be described below.

(1) Photosensitivity Evenness

Image formation was conducted using a whole halftone original toreproduce image samples. Of the resultant image samples, the worstsample in terms of the density evenness was dedicated for the evaluationof the photosensitivity evenness of the photosensitive member in thefollowing manner.

That is, nine equal square regions were apparently established at thesurface of the photosensitive member by axially dividing the surfaceinto three equal parts and circumferentially dividing the surface intothree equal parts. And the optical density of each of the correspondingnine square regions on the image sample was examined, and a mean valueamong the resultant nine optical densities was obtained. Then, theoptical density of each square region was compared with the mean value.Based on the compared results, evaluation was made in accordance withwas the following criteria. The evaluated result is shown in the table.

⊚: no substantial difference is recognized among the nine squareregions,

∘: a slight difference is recognized as for one or two of the ninesquare regions,

Δ: all the square regions are different but their different magnitude isslight, and

X: problematic differences are present among the nine square regions.

(2) Resolution

Image formation was conducted using an original having minute characterson a white background to reproduce image samples. As for the resultantimage samples, examination was made of whether or not the imagesreproduced are equivalent to the minute characters of the original. Ofthe image samples, the worst one is shown in the table based on thefollowing criteria.

⊚: excellent in resolution,

∘: slightly crashed parts are present,

Δ: many apparently crashed parts are present but the reproducedcharacters can be recognized, and

x: markedly crashed parts are present and wherein some of the reproducedcharacters are hardly recognized.

(3) Appearance of Interference Fringe Pattern

Evaluation was made of whether or not the photosensitive member isliable to provide an interference infringe patter on an image reproduceddue to the presence of an unevenness in the thickness of the lightreceiving layer. That is, image formation was conducted using a wholehalftone original and a solid black original in combination to reproduceimage samples. The resultant image samples were evaluated based on thefollowing criteria. The evaluated result is shown in the table.

⊚: no interference fringe pattern is found in any of the image samples,

∘: a slight interference fringe pattern is found in some of the halftoneimage samples,

Δ: a distinguishable interference fringe pattern is found in all thehalftone image samples but not in the solid black image samples, and

X: a distinct interference fringe pattern is found in any of the imagesamples.

(4) Appearance of Coarseness

Evaluation was made of whether or not the photosensitive member isliable to provide a coarseness on an image reproduced. That is, imageformation was conducted by using a whole halftone original and anoriginal having minute characters on a white background in combinationto reproduce image samples. The resultant image samples were evaluatedbased on the following criteria. The evaluated result is shown in thetable.

⊚: no coarseness is found in any of the image samples,

∘: a slight coarseness is found in some of the halftone image samples,

Δ: a distinct coarseness is found in any of the halftone image samplesbut no coarseness is found in any of the image samples reproduced fromthe character original, and

X: a distinct coarseness is found also in any of the image samplesreproduced from the character original wherein some of the reproducedcharacters are hardly recognized.

From the results shown in Table 2, it is understood that in the casewhere the photosensitive member is designed to have a light receivinglayer comprising a deposited film containing a plurality of columnarstructure regions formed at a given density in the range of 5/cm² to500/cm² therein, it exhibits markedly improved electrophotographiccharacteristics, particularly with respect to occurrence of unevendensity, resolution, appearance of an interference fringe pattern, andappearance of a coarseness for an image reproduced.

Based on the results obtained in the above Experiments 1 to 4, there wasobtained a finding that in the case of forming a layer composed of anon-single crystal material on a substrate, depositing on the surface ofthe layer a plurality of particles each capable of being a crystalnucleus for growing a columnar structure region therefrom in immobilizedstate, and additionally forming a layer composed of a non-single crystalmaterial thereon while growing a plurality of columnar structure regionsbased on the respective crystal nucleuses at a given density in therange of 5/cm² to 500/cm² and substantially in parallel to thethicknesswise direction, there is afforded a light receiving memberwhich exhibits markedly improved electrophotographic characteristics,particularly with respect to occurrence of uneven density, resolution,appearance of an interference fringe pattern, and appearance of acoarseness for an image reproduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A) through 1(E) are schematic cross sectional views eachillustrating an example of an electrophotographic photosensitive memberaccording to the present invention.

FIG. 1(F) is a schematic view showing incident path and reflection pathof rays of light in an electrophotographic photosensitive memberaccording to the present invention.

FIGS. 2(A) and 2(B) are schematic diagrams illustrating a film-formingapparatus suitable for the production of an electrophotographicphotosensitive member according to the present invention.

FIG. 3 and FIG. 4 are schematic diagrams each illustrating a polishingapparatus used in the present invention.

FIG. 5 is a schematic cross sectional view illustrating a conventionalelectrophotographic photosensitive member.

FIGS. 6(A) and 6(B) are schematic diagrams illustrating a microwaveplasma CVD apparatus.

FIG. 7 is a schematic diagram illustrating a RF plasma CVD apparatus.

FIG. 8 is a schematic diagram illustrating a polishing apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An aspect of the present invention is directed to an electrophotographicphotosensitive member comprising a substrate and a light receiving layercomposed of a non-single crystal material containing silicon atoms as amatrix disposed on said substrate, characterized in that said lightreceiving layer contains a plurality of columnar structure regions eachgrown from a given nucleus situated within said light receiving layerwherein said plurality of columnar structure regions are arrangedsubstantially in parallel to the thicknesswise direction of said lightreceiving layer and at a density in the range of 5/cm² to 500/cm².

Another aspect of the present invention is directed to a process forproducing an electrophotographic photosensitive member by introducing agaseous silicon-containing raw material into a substantially enclosedreaction chamber having a discharge space, and supplying a microwaveenergy into the reaction chamber to generate a plasma in the dischargespace to thereby form a film composed of a silicon-containing non-singlecrystal material as a light receiving layer on a substrate positioned inthe reaction chamber, characterized by comprising the steps of:

(i) forming a film as a partial layer region of said light receivinglayer,

(ii) spacedly depositing a plurality of nucleuses, each capable of beinga nucleus for growing a columnar structure region based on said nucleus,on the surface of said film in an immobilized state, and

(iii) repeating the film-forming step (i) to form a film on the surfaceof said film having said plurality of nucleuses thereon while growing acolumnar structure region based on each of said plurality of nucleuseswhereby a plurality of columnar structure regions are formedsubstantially in parallel to the thicknesswise direction and at adensity in the range of 5/cm² to 500/cm².

In the following, description will be made of the electrophotographicphotosensitive member according to the present invention with referenceto FIG. 1(A).

In FIG. 1(A), reference numeral 102 indicates a substrate, and referencenumeral 104 indicates a layer capable of functioning as aphotoconductive layer which is composed of a non-single crystal material(specifically, an amorphous, microcrystalline or polycrystallinematerial) containing silicon atoms as a matrix. Reference numeral 110indicates a columnar structure region, and reference numeral 111indicates a nucleus for said columnar structure region. Referencenumeral 103 indicates a charge injection inhibition layer, and referencenumeral 105 indicated a surface layer. The charge injection inhibitionlayer 103 and the surface layer 105 are not always necessary to bedisposed, and these layers may be optionally disposed depending upon thecharacteristics desired for an electrophotographic photosensitive memberto be obtained.

The electrophotographic photosensitive member according to the presentinvention is free of the problems such as occurrence of uneven imagedensity and deterioration in resolution which are found in theconventional electrophotographic photosensitive member and stably andcontinuously exhibits excellent image-forming characteristics. Thissituation will be described while referring to FIG. 1(F).

FIG. 1(F) is a schematic view for explaining how light travels when thelight is impinged into the photoconductive layer 104 composed of anon-single crystal material containing silicon atoms as a matrix. InFIG. 1(F), each columnar structure region 110 and each nucleus 111 forthe columnar structure region establish respective interfaces in thenon-single crystal material layer 104. The refractive index of thecolumnar structure region 110 is different from that of the non-singlecrystal material layer region 104, and because of this, ray of incidentlight I₁ is repeatedly reflected at the interface between these regionsto provide reflected rays R₁ to R₆. The reflected rays R₁ to R₆ have adifferent optical path length respectively, and because of this, theyinterfere with each other to strengthen or weaken their intensity,wherein however, the presence of the columnar structure regions 110makes those rays to more frequently reflect whereby the opportunitiesfor the rays to interfere with each other are distributed to prevent therays from being strengthened or weakened at a specific position.

Further, in the electrophotographic photosensitive member, a chargeGenerated in the photoconductive layer upon subjecting it to exposureare prevented from being pulled and drifted by virtue of an electricfield of the residual charge in the non-exposed portion because of thepresence of the columnar structure regions 110.

In the electrophotographic photosensitive member of the presentinvention, the layer 104 composed of a non-single crystal materialcontaining silicon atoms as a matrix may be of a stacked structurecomprising a plurality of layers, for example, layers 104(A), 104(B) and104(C) as shown in FIG. 1(B). Similarly, each of the layer 103 and thelayer 105 may be of a stacked structure comprising a plurality of layerseach being different in terms of the chemical composition.Alternatively, the layer 103 and the layer 105 may be designed such thatthe former functions as a light absorption layer capable of preventinglight from being reflected from the substrate or a charge transportationlayer, and the latter functions as a charge generation layer. In apreferred embodiment, the layer 103 is designed to function as a lightabsorption layer and/or a charge injection inhibition layer, and thelayer 105 is designed to function as a charge Generation layer and/or asurface layer. Specifically, the layer 103 and the layer 105 may becomposed of a material selected from the group consisting of non-singlecrystal materials (including amorphous and polycrystalline materials)containing silicon atoms as a matrix, and one or more kinds of atomsselected from the group consisting of carbon, germanium, nitrogen,oxygen, hydrogen, fluorine, boron, and phosphorous atoms.

As for the columnar structure region formed in the light receiving layerin the present invention, it is configured to have a circular shape, anelliptical shape or other shape comprising these shapes being overlappedin terms of the cross-sectional shape provided when the columnarstructure region-containing light receiving layer is cut in thedirection horizontal to the free surface thereof. In addition, as forthe cross-sectional shape of the columnar structure region provided whenthe columnar structure region-containing light receiving layer is cut inthe direction perpendicular to the free surface thereof, it is desiredto be of a rectangular shape, a triangular shape, a trapezoidal shape,or other shape comprising a combination of these shapes.

As for the size of the columnar structure region, it is desired to bepreferably in the range of 1 μm to 300 μm or more preferably in therange of 5 μm to 100 μm in terms of the diameter (or the major axis)when looked from the free surface side of the light receiving layer. Inthe case where the columnar structure region is of a size of less thanthe above lower limit, the effects of the present invention are notprovided as desired. On the other hand, in the case where it is of asize of exceeding the above upper limit, desirable electrophotographiccharacteristics are not provided.

In a preferred embodiment of the present invention, a plurality ofcolumnar structure regions each having any of the above-described shapesand having a size of 5 μm to 100 μm in terms of the diameter (or themajor axis) are formed to arrange substantially in parallel to thethicknesswise direction at a given density preferably in the range of5/cm² to 500/cm², more preferably in the range of 10/cm² to 300/cm² mostpreferably in the range of 10/cm² to 100/cm² in the light receivinglayer. In the case where the density for the columnar structure regionsto be arranged is less than the above lower limit, the effects of thepresent invention are not provided as desired. On the other hand, in thecase where it exceeds the above upper limit, desirableelectrophotographic characteristics are not provided, wherein defectsincluding occurrence of coarseness and the like entail for an imagereproduced.

In the present invention, as the nucleus for growing the columnarstructure region based on it, any material can be used as long as it isa fine particle. However, it is preferred to use a powder of acrystalline material such a silicon-containing single crystal materialor a silicon-containing polycrystalline material. Alternatively, it ispossible to use a powder of a non-single crystal material.

In the present invention, the position at which the columnar structureregion starts growing in the light receiving layer is an importantfactor. It is desired to be set at the position which is distantpreferably by 1 μm or more, more preferably by 3 μm or more, mostpreferably 5 μm or more, from the position where the lower interfacethereof is situated in the thicknesswise direction.

In order to form a plurality of the foregoing columnar structure regionsin the light receiving layer, as previously described, a given depositedfilm is firstly formed and then, a plurality of nucleuses for growingthe columnar structure regions are spread over the deposited film todeposit them on the surface of the deposited film. In a preferredembodiment of the manner of doing this, those nucleuses are firstlyelectrically charged, the electrically charged nucleuses are thenintroduced into the reaction chamber together with rare gas such ashelium gas, neon gas or argon gas, hydrogen gas, or film-forming rawmaterial gas such as silane gas or methane gas to spread them over thedeposited film wherein they are deposited on the surface of thedeposited film in immobilized state by virtue of an electric fieldgenerated between the electrically charged nucleuses-and the substrate.

To make fine particles as the nucleuses electrically charged may beconducted by means of a conventional charge-imparting manner such ascorona discharge, spark discharge or glow discharge technique.Specifically, for instance, in the case where the corona dischargetechnique, the fine particles can be electrically charged by using acharger provided with a charging wire comprising s stainless steel ortungsten wire of 0.1 to 0.5 mm in diameter and applying a D.C. voltageof 4 to 8 V to the charger to thereby cause corona discharge.

The fine particles bearing charges thus obtained are introduced into thereaction chamber by spouting them thereinto at an appropriate spoutingpressure by the aid of any of the foregoing gases which is flown at agiven flow rate. The flow rate of the gas and the pressure for thecharge-bearing fine particles to be spouted should be properlydetermined depending upon the related conditions including the size andamount of the charge-bearing fine particles, the surface area of thefilm on which the charge-bearing fine particles are to be spread and theperiod of time during which the charge-bearing fine particles arespread. However, in general, it is desired that the flow rate of the gasis in the range of 100 sccm to 100 slm and the spouting pressure is inthe range of 10⁴ Pa to 10⁵ Pa.

And in order to deposit the charge-bearing fine particles on the surfaceof a given deposited film by virtue of an electric field generatedbetween the charge-bearing fine particles and the substrate, theintensity of the electric field is desired to be in the range of 1 V/cmto 100 V/cm.

In the present invention, the silicon-containing non-single crystalmaterial by which the layer 104 is constituted is desired to containcarbon atoms in an amount of 2.0 atomic % to 25 atomic % versus theamount of the silicon atoms and fluorine atoms in an amount of 2 atomicppm to 90 atomic ppm versus the amount of the silicon atoms.

The silicon-containing non-single crystal material layer 104 may beformed by using, in addition to a silicon atom-imparting raw materialgas such as silane and disilane, a carbon atom-imparting raw materialgas selected from the group consisting of methane (CH₄), ethane (C₂ H₅),ethylene (C₂ H₄), acetylene (C₂ H₂), propane (C₃ H₈) and mixtures ofthese gases. Alternatively, it is possible to use tetramethylsilane(Si(CH₃)₄) capable of imparting silicon and carbon atoms at the sametime. In order to incorporate fluorine atoms into the silicon-containingnon-single crystal material layer 104, there is used a gaseous fluoridesuch as silicon tetrafluoride (SiF₄), carbon tetrafluoride (CF₄) and amixture of these.

In a preferred embodiment of the amount of the carbon atoms contained inthe layer 104, it is preferably in the range of 2 atomic % to 20 atomic%, most preferably in the range of 3 atomic % to 10 atomic %,respectively versus the amount of the silicon atoms contained in thelayer 104.

In a preferred embodiment of the amount of the fluorine atoms containedin the layer 104, it is preferably in the range of 2 atomic ppm to 90atomic ppm, most preferably in the range of 3 atomic ppm to 80 atomicppm versus the amount of the silicon atoms contained in the layer 104.

The layer 104 is desired to be of a thickness preferably in the range of30% to less than 100%, more preferably in the range of 50% to less than100%, versus the total layer thickness on the substrate.

In the present invention, the layer 104 may be desirably formed by meansof the microwave plasma CVD technique. In this case, it is effective toconduct film formation while applying a desired bias voltage in thedischarge space such that an electric field is caused at least in thedirection in which a positive ion collides with the substrate. In thecase where no bias voltage is applied upon the film formation, theeffects of the present invention are not provided as desired.

The above bias voltage can include a voltage of D.C. The D.C. voltageapplied is desired to be preferably in the range of 1 V to 500 V, morepreferably in the range of 5 V to 100 V.

The formation of each of the layer 103 and the layer 105 may beconducted by means of the vacuum evaporation, sputtering,thermal-induced CVD, or plasma CVD technique.

The substrate used in the present invention can include, for example,metals such as stainless steel, Al, Cr, Mo, Au, In, Nb, Te, V, Ti, Pt,Pd, and Fe, alloys of these metals, members of synthetic resins such aspolycarbonate and the like, glass, ceramics and papers which have beenapplied with electroconductive treatment to their surface.

The substrate may be of any configuration, which can be properlydetermined depending upon the application uses. However, in the casewhere the formation of the light receiving layer is conducted in amanner in which discharge is caused in the discharge space circumscribedby a plurality of substrates on each of which a film is to be formed,each substrate is desired to be cylindrical. In this case, there is noparticular restriction for the size for the cylindrical substrate.However in a preferred embodiment in terms of practical applications,the cylindrical substrate is made to be of a size of 20 mm to 500 mm indiameter and 10 mm to 1000 mm in length.

In the above film-forming manner in which the discharge space iscircumscribed by a plurality of cylindrical substrates, the cylindricalsubstrates are desired to be spacedly arranged while leaving a desiredspacing of 1 mm to 50 mm between each adjacent cylindrical substrates.There is no particular restriction for the number of the cylindricalsubstrates arranged as long as they can establish a desired dischargespace circumscribed by them. However, in general, the number of thecylindrical substrates arranged is at least 3, preferably 5 or more.

In the present invention, as particularly desirable examples of thesilicon-containing non-single crystal material constituting the abovelayer, there can be mentioned amorphous materials each containingsilicon atoms as a matrix and at least hydrogen atoms, and otheramorphous materials each containing silicon atoms as a matrix and otherappropriate atoms.

In the electrophotographic photosensitive member of the presentinvention, the total layer thickness on the substrate is desired to bepreferably in the range of 5 μm to 100 μm, more preferably in the rangeof 10 μm to 70 μm, most preferably in the range of 15 μm to 50 μm.

The formation of the light receiving layer of the electrophotographicphotosensitive member may be desirably conducted by means of the plasmaCVD technique. The plasma CVD technique herein can include DC glowdischarge decomposition process, RF glow discharge decompositionprocess, and microwave glow discharge decomposition process. Of theseprocesses, the microwave glow discharge decomposition process is themost desirable.

In the case of the microwave discharge decomposition process, as shownin FIGS. 2(A) and 2(B), a plurality of substrates are arranged so as toestablish a discharge space and a microwave energy is introduced intothe discharge space at lest from one end side of the arrangement of thesubstrates. In this case, the microwave energy is introduced through themicrowave introducing dielectric window. The dielectric window isconstituted by a dielectric material capable of allowing a microwaveenergy to transmit therethrough without being leaked such as alumina(Al₂ O₃), aluminum nitride (AlN), boron nitride (BN), silicon nitride(SIN), silicon carbide (SIC), silicon oxide (SiO₂), beryllium oxide(BeO), Teflon, and polystyrene.

The gas pressure in the discharge space upon film formation by usingeither a D.C. power or RF power as the discharging power is desired tobe preferably in the range of 100 mTorr to 5 Torr, more preferably inthe range of 200 mTorr to 2 Torr. In the case of conducting the filmformation by using a microwave power as the discharging power, it isdesired to be preferably in the range of 0.5 mTorr to 100 mTorr, morepreferably in the range of 1 mTorr to 50 mTorr in order to attain stabledischarging and to ensure a desirable uniformity for a film formed.

As for the substrate temperature upon film formation, a temperature inthe range of 100° C. to 500° C. may be employed. However in practice, itis preferably in the range of 150° C. to 450° C., more preferably in therange of 200° C. to 400° C., most preferably in the range of 230° C. to350° C.

The substrate may be heated to a desired temperature by means of aconventional heating means. Specific examples of such heating means areelectric resistance heat generating means such as sheath-like heater,spiral heater, plate-like heater, and ceramics heater, heat radiationlamp heating means such as halogen lamp, and infrared ray lamp, and heatexchanging mechanisms in which liquid or air is used as a heat transfermedium.-In any case, the heating means is designed to have a surfacecomposed of a metal such stainless steel, nickel, aluminum, or copper,or other material such as ceramic, or heat resistant resin.

Instead of the above heating means, it is possible to take a manner inwhich the substrate is heated in an independent heating vessel situatedseparately from the reaction chamber and it is transferred into thereaction chamber under vacuum condition. Alternatively, in the case ofusing a microwave energy for the film formation, it is possible tocontrol the substrate temperature by virtue of the energy from themicrowave energy, wherein for instance, the intensity of the microwaveapplied is properly controlled.

These heating means and manners may be used either singly or incombination of two or more of them.

As for the discharging power upon film formation in the case of usingeither a D.C. power or RF power, it is preferably in the range of 20 Wto 2 kW, more preferably in the range of 50 W to 1 kW. In the case ofusing a microwave power, it is preferably in the range of 100 W to 10kW, more preferably in the range of 500 W to 2 kW.

In the present invention, the foregoing surface polishing treatment maybe employed if necessary, wherein the use of an abrasive tape appliedwith fine particles of an abrasive to the surface thereof isparticularly effective. Specific examples of the abrasive are silica(SiO₂), alumina (Al₂ O₃), iron oxide (Fe₂ O₃), silicon carbide (SIC),carbon nitride (C₃ N₄), and cerium oxide (CeO), respectively in the fineparticle powdery form. As for the abrasive used, a due care should bemade about its mean particle size, because if the abrasive is of aexcessively small mean particle size, a problem entails in that it isdifficult to attain a high polishing rate and because of this, it takesa relatively long period of time to complete the surface polishingtreatment, and if the abrasive is of an excessively large mean particlesize, a problem entails in that the polishing rate is markedlyheightened to provide a polishing influence to other portions than theprotrusions from the columnar structure regions. In view of this, theabrasive is desired to be of a mean particle size in the range of 1 μmto 20 μm.

The above abrasive tape comprises a film-like base member applied withfine particles of any of the foregoing abrasives to the surface thereof.Specific examples of such film-like base member are thin films of highpolymeric organic substances such as polyamide, polyester, polyurethane,polyurea, polyolefin, polystyrene, polyvinyl chloride, polyvinylidenechloride, polyethylene, fluoride, polyacrylonitrile, polyvinyl alcohol,and polyvinylidene cyanide; thin films of metals such a stainless steel,and the like; and papers. Among these, the high polymeric organicsubstance films are the most desirable for the reasons that they arelightweight, have strength, and resistant to environmental variation,and in addition, they can be mass-produced.

In the surface polishing treatment, the foregoing polishing apparatusmay be used. The pressure roller used in the polishing apparatus may becomposed of an appropriate material. However, in the case where thepressure roller is excessively hard, there is a tendency that thesurface of an electrophotographic photosensitive member as an object tobe treated is excessively ground by the abrasive tape and as a result,it is damaged. On the other hand, in the case where the pressure rolleris excessively soft, the abrasive tape is not sufficiently pressedagainst the surface of the photosensitive member to be treated andbecause of this, a desirable polishing rate is hardly attained. In orderto prevent occurrence of these problems, the pressure roller is desiredto be one having a coat composed an elastic material such as siliconrubber or urethane rubber. In addition, it is desired for the pressureroller to be such that enables to establish a relevant nip width betweenthe abrasive tape and the photosensitive member to be treated dependingupon the magnitude of the pressure applied. The nip width herein isdesired to be in the range of 0.01 mm to 3 mm. The pressure applied tothe abrasive tape upon the surface polishing treatment is desired to bein the range of 10 g/cm to 500 g/cm in terms of linear pressure.

Alternatively, instead of the above pressure roller, it is possible touse a curved pressure member having a convex surface.

In the present invention, instead of the above described abrasive, it ispossible to use a dispersion comprising an abrasive material dispersedin a solvent as the abrasive is effective. The abrasive material usablein this case can include silica (SiO₂), alumina (Al₂ O₃), iron oxide(Fe₂ O₃), silicon carbide (SIC), carbon nitride (C₃ N₄), and ceriumoxide (CeO), respectively in the fine particle powdery form. As for theabrasive material used, a due care should be made about its meanparticle size, because if the abrasive material is of a excessivelysmall mean particle size, a problem entails in that it is difficult toattain a high polishing rate and because of this, it takes a relativelylong period of time to complete the surface polishing treatment, and ifthe abrasive material is of an excessively large mean particle size, aproblem entails in that the polishing rate is markedly heightened toprovide a polishing influence to other portions than the protrusionsfrom the columnar structure regions of the photosensitive member to betreated. In view of this, the abrasive material is desired to be of amean particle size in the range of 1 μm to 20 μm.

As the above solvent, it is possible to use any of the conventionalsolvents as long as the above abrasive material can be dispersed thereinas desired. However, in view of ease in handling, water is the mostappropriate. As for the content of the abrasive material in thedispersion, it is desired to be in the range of 5% to 50% in terms ofvolume percentage.

The dispersion comprising any of the above abrasive material dispersedin a given solvent is supported on an appropriate support member. Assuch support member, any support member may be used in this case as longas it is capable of supporting the suspension thereon. Specific examplesare fibrous materials such as fabrics and papers. As for the shape ofthe support member, there is no particular restriction. Specifically, itmay be configured to be in the form of a roller-like shape, a planeshape or other shape having a curved face capable of encapsulating anelectrophotographic photosensitive member in the form of a cylindricalshape. In the surface polishing treatment using such abrasive member,the nip width is desired to be in the range of 0.1 mm to 100 mm. Thepressure applied to the abrasive member upon the surface polishingtreatment is desired to be in the range of 1 g/cm² to 1000 g/cm².

In any case, the electrophotographic photosensitive member to besubjected to surface polishing treatment is rotated at a rotation speedof 1 mm/sec. to 1000 mm/sec. And the period of time during which theelectrophotographic photosensitive member is subjected to surfacepolishing treatment is desired to be preferably a period of 10 secondsto 60 minutes, more preferably a period of 1 minute to 10 minutes.

In the present invention, observation of the cross section structure ofa deposited film formed as the light receiving layer can be conducted bycutting the deposited film to obtain a sample having a cross sectionface, if necessary, polishing the cross section face by a conventionalbuffing technique, and observing the cross section face by means of aconventional optical microscope or electron microscope.

In the following, the electrophotographic photosensitive member and theprocess for the production thereof according to the present inventionwill be described in more detail with reference to examples. It shouldbe understood that the scope of the present invention is not restrictedto these examples only.

EXAMPLE 1

There were prepared plural kinds of amorphous silicon seriesthree-layered electrophotographic photosensitive members each having theconfiguration shown in FIG. 1(A) using the same film-forming apparatusas used in Experiment 4. As for each electrophotographic photosensitivemember, a plurality of electrophotographic photosensitive member sampleswere prepared by repeating the film-forming procedures under theconditions shown in Table 1 in Experiment 4, except that the flow rateof the CH₄ gas upon forming the layer 104 was varied in each case andthe step of spreading the Si-power was conducted by introducingSi-powder of 10 μm in mean particle size together with Ar gas into thereaction chamber 201 through the supply ports 213 for 2 minutes underconditions of 2.5×10⁴ Pa for the spouting pressure of the Si powder and1000 sccm for the flow rate of the Ar gas.

As for each of the resultant electrophotographic photosensitive members,evaluation was conducted in the same manner as in Experiment 4.

The evaluated results obtained are collectively shown in Table 4.

The evaluation with respect to appearance of while spots described inTable 4 was conducted in the following manner.

Evaluation of White Spot Appearance:

Image formation is conducted using a solid black original to reproduceimage samples. The resultant image samples are evaluated by counting thenumber of white spots in a given area. Of the image samples, the worstone is shown in the table based on the following criteria.

⊚: presence of no distinguishable white spot,

∘: presence of a few distinguishable small white spots,

Δ: presence of a number of white spots on the entire area butpractically acceptable, and

X: presence of remarkable white spots and practically problematic.

From the results shown in Table 4, it is understood that theelectrophotographic photosensitive members belonging to the presentinvention in which the amount of carbon atoms contained in the layer 104is in the range of 2.0 atomic % to 25 atomic % excel in theelectrophotographic characteristics.

EXAMPLE 2

There were prepared plural kinds of amorphous silicon seriesthree-layered electrophotographic photosensitive members each having theconfiguration shown in FIG. 1(A) using the same film-forming apparatusas used in Experiment 4. As for each electrophotographic photosensitivemember, a plurality of electrophotographic photosensitive member sampleswere prepared by repeating the film-forming procedures under theconditions shown in Table 1 in Experiment 4, except that the flow rateof the SiF₄ gas upon forming the layer 104 was varied in each case andthe step of spreading the Si powder was conducted by introducing Sipowder of 10 μm in mean particle size together with Ar gas into thereaction chamber 201 through the supply ports 213 for 2 minutes underconditions of 2.5×10⁴ Pa for the spouting pressure of the Si-powder and1000 sccm for the flow rate of the Ar gas.

As for each of the resultant electrophotographic photosensitive members,image formation was conducted and evaluated was conducted with respectto photosensitivity evenness and resolution in the same manner as inExperiment 4.

The evaluated results obtained are collectively shown in Table 5.

From the results shown in Table 5, it is understood that theelectrophotographic photosensitive members belonging to the presentinvention in which the amount of fluorine atoms contained in the layer104 is in the range of 2.0 atomic ppm to 90 atomic ppm excel in theelectrophotographic characteristics.

Separately, it was found that the same tendency as in the above isprovided in the case where the amount of the carbon atoms contained inthe layer 104 is properly varied.

EXAMPLE 3

There were prepared plural kinds of three-layered amorphous siliconseries electrophotographic photosensitive members each having theconfiguration shown in FIG. 1(D) by repeating the procedures ofExperiment 4 under the conditions shown in Table 6, wherein theelectrophotographic photosensitive members were made different from eachother by varying the thickness of each of the layer 104(B) and the layer105 and varying the total layer thickness on the substrate to a value of20 μm, 30 μm and 40 μm. In each case, upon forming the layer 104(A), CH₄gas and SiF₄ gas were introduced into the reaction chamber at respectiveflow rates capable of making the amount of the carbon atoms containedtherein to be 14 atomic % versus the amount of the silicon atomscontained therein and the amount of the fluorine atoms contained thereinto be 70 atomic ppm versus the amount of the silicon atoms containedtherein, and upon forming the layer 104(B), CH₄ gas and SiF₄ gas wereintroduced into the reaction chamber at respective flow rates capable ofmaking the amount of the carbon atoms contained therein to be 7 atomic %versus the amount of the silicon atoms contained therein and the amountof the fluorine atoms contained therein to be 30 atomic ppm versus theamount of the silicon atoms contained therein. And in each case, thestep of spreading the nucleuses for growing a plurality of columnarstructure regions was conducted after having formed a deposited film asthe layer 104(B) at a thickness of 5 μm, in the same manner as inExperiment 4. As for each of the resultants, evaluation was conducted inthe same manner as in Experiment 4. The evaluated results obtained arecollectively shown in Table 7.

From the results shown in Table 7, it is understood that theelectrophotographic photosensitive members belonging to the presentinvention in which the layer 104 has a thickness of greater than 30% butless than 100% versus the total layer thickness on the substrate excelin the electrophotographic characteristics.

Separately, it was found that the same tendency as in the above isprovided in the case where the amount of each of the carbon and fluorineatoms contained in the layer 104 is properly varied.

EXAMPLE 4

The procedures of Experiment 4 were repeated, except that thefilm-forming conditions were changed to those shown in Table 8 and thatthe step of spreading the Si-powder was conducted by introducing Sipowder of 10 μm in mean particle sized together with Ar gas into thereaction chamber 201 through the supply ports 213 for 2 minutes underconditions of 2.5×10⁴ Pa for the spouting pressure of the Si powder and1000 sccm for the flow rate of the Ar gas, to thereby obtain a pluralityof electrophotographic photosensitive member samples. The resultantelectrophotographic photosensitive member samples were evaluated in thesame manner as in Experiment 4. The evaluated results obtained arecollectively shown in Table 10. These electrophotographic photosensitivemember samples were evaluated also with respect to minute linereproducibility, cleaning suitability, durability, and maintenance load,respectively in the following manner. The evaluated results obtainedwith respect to these evaluation items are also collectively shown inTable 10.

Minute Line Reproducibility:

Image formation was conducted using an original having minute characterson a white background to reproduce image samples. As for each imagesample, evaluation was conducted of whether or not the minute lines ofthe original are reproduced without being broken as desired, whereinappearance of uneven image was also observed. 0f the image samples, theworst one was shown in the table based on the following criteria.

⊚: excellent in minute line reproduction,

∘: slightly broken parts are present,

Δ: a number of broken parts are present but the characters can bedistinguished, and

X: markedly broken parts are present and some of the characters cannotbe distinguished.

Cleaning Suitability:

There were provided three originals, i.e., a solid black original, ahalftone original, and a character original. Image formation wasrepeatedly conducted ten times using each of these originals to obtainimage samples. Based on the resultant image samples, cleaningsuitability was evaluated as for the electrophotographic photosensitivemember sample used, in accordance with the following criteria. Theevaluated result obtained was shown in the table.

⊚: excellent in cleaning suitability,

∘: a slight cleaning defect is present,

Δ: some stripe-like cleaning defects are present but they are notproblematic in practice, and

X: remarkable cleaning defects are present.

Durability:

The electrophotographic photosensitive member sample having beensubjected to the above evaluations was subjected to 10,000 timescontinuous copying shots in a conventional electrophotographic copyingmachine, and thereafter, the electrophotographic photosensitive memberwas evaluated with respect to each of the foregoing evaluation itemsbased on the following criteria. The evaluated result obtained was shownin the table.

⊚: the results as for all the evaluation items are satisfactory as wellas those at the initial stage,

∘: the result as for one of the evaluation items is slightly inferior tothat at the initial state,

Δ: the results as for some of the evaluation items are distinguishablyinferior to those at the initial stage, but they are practicallyacceptable, and

X: the results as for all the evaluation items are markedly inferior andthey are problematic in practice.

Maintenance Load:

The electrophotographic photosensitive sample was subjected tocontinuous copying shots in a conventional electrophotographic copyingmachine until cleaning defects due to occurrence of a damage at thecleaning blade were appeared or papers were not satisfactorily separatedbecause of wear-out failure at the separating pawl. And the number ofpapers fed therein was compared with that when the periodic maintenancecheck is usually conducted for the copying machine. The result wasevaluated based on the following criteria. The evaluated result obtainedwas shown in the table.

⊚: the number of papers fed is markedly greater than that when theperiodic maintenance check is conducted,

∘: the number of papers fed is slightly grater than that when theperiodic maintenance check is conducted,

Δ: the number of papers fed is smaller than that when the periodicmaintenance check is conducted, and

X: the number of papers fed is markedly smaller than that when theperiodic maintenance check is conducted.

COMPARATIVE EXAMPLE 1

Using the film-forming apparatus shown in FIGS. 6(A) and 6(B), therewere prepared a plurality of electrophotographic photosensitive membersamples without having any columnar structure regions under theconditions shown in Table 3. The resultant electrophotographicphotosensitive member samples were evaluated in the same manner as inExample 4. The evaluated results obtained are collectively shown inTable 10.

COMPARATIVE EXAMPLE 2

There were prepared a plurality of amorphous silicon serieselectrophotographic photosensitive member samples having theconfiguration shown in FIG. 5 by means of the RF plasma CVD processunder the conditions shown in Table 9.

Herein, in FIG. 5, reference numeral 502 indicates an Al substrate,reference numeral 503 indicates a charge injection inhibition layer,reference numeral 504 indicates a photoconductive layer, and referencenumeral 505 indicates a surface layer.

Each electrophotographic photosensitive member was prepared using afilm-forming apparatus of the constitution shown in FIG. 7, wherein therespective amorphous silicon films were formed on the Al substrate 705in the conventional manner.

In FIG. 7, reference numeral 701 indicates a reaction chamber, referencenumeral 702 indicates a RF power source, reference numeral 703 indicatesa raw material gas feed pipe, reference numeral 706 indicates adischarge space, reference numeral 707 indicates a holding member,reference numeral 708 indicates an insulator, and reference numeral 709indicates a rotary shaft.

Each of the resultant electrophotographic photosensitive member sampleswas subjected to surface polishing treatment using a polishing apparatus801 of the constitution shown in FIG. 8. In the surface polishingtreatment using this polishing apparatus, the electrophotographicphotosensitive member sample 805 was positioned on rotary shaft 806, andit was rotated by means of motor 811 while press-contacting an abrasivecloth 807 applied with a dispersion of powdery silica of 2 μm in meanparticle size dispersed in normal heptane to the surface thereof to thesurface of the photosensitive member sample 805 by means ofpress-contacting mechanism 802, whereby the surface of thephotosensitive member sample was polished.

The electrophotographic photosensitive member samples thus treated wereevaluated in the same manner as in Example 4. The evaluated resultsobtained are collectively shown in Table 10.

EXAMPLE 5

Using the same film-forming apparatus as used in Experiment 4, therewere prepared a plurality of four-layered electrophotographicphotosensitive member samples each having the configuration shown inFIG. 1(E) by repeating the procedures of Experiment 4 under theconditions shown in Table 11, wherein the step of spreading the Sipowder as the nucleuses for growing a plurality of columnar structureregions was conducted by introducing, after having formed a depositedfilm as the layer 104 at a thickness of 5 μm, Si powder of 12 μm in meanparticle sized together with Ar gas into the reaction chamber 201through the supply ports 213 for 2 minutes under conditions of 2.5×10⁴Pa for the spouting pressure of the Si powder and 800 sccm for the flowrate of the Ar gas. The resultant electrophotographic photosensitivemember samples were evaluated in the same manner as in Example 4. As aresult, the electrophotographic photosensitive member samples were foundto be excellent in the electrophotographic characteristics as well asthe electrophotographic photosensitive member samples obtained inExample 4.

EXAMPLE 6

Using the same film-forming apparatus as used in Experiment 4, therewere prepared a plurality of three-layered electrophotographicphotosensitive member samples each having the configuration shown inFIG. 1(A) by repeating the procedures of Experiment 4, except that thefilm-forming conditions were changed to those shown in Table 12 whereinacetylene gas was used instead of the methane gas as the carbonatom-supplying source upon forming the layer 104 and that the step ofspreading the Si powder as the nucleuses for growing a plurality ofcolumnar structure regions was conducted by introducing, after havingformed a deposited film as the layer 104 at a thickness of 4 μm, Sipowder of 12 μm in mean particle sized together with Ar gas into thereaction chamber 201 through the supply ports 213 for 3 minutes underconditions of 2.5×10⁴ Pa for the spouting pressure of the Si powder and800 sccm for the flow rate of the Ar gas. The resultantelectrophotographic photosensitive member samples were evaluated in thesame manner as in Example 4. As a result, the electrophotographicphotosensitive member samples were found to be excellent in theelectrophotographic characteristics as well as the electrophotographicphotosensitive member samples obtained in Example 4.

EXAMPLE 7

Using the film-forming apparatus, the procedures of Example 4 wererepeated under the film-forming conditions shown in Table 8 to therebyobtained a plurality of electrophotographic photosensitive membersamples.

Each of the resultant electrophotographic photosensitive member sampleswas subjected to surface treatment using a polishing apparatus of theconstitution shown in FIG. 4. The polishing apparatus shown in FIG. 4 isof the type that an electrophotographic photosensitive member to betreated is set to a rotary shaft the rotary shaft is rotated whilesupplying an abrasive liquid 413 to the surface of theelectrophotographic photosensitive member on the rotary shaft, wherebythe surface of the electrophotographic photosensitive member ispolished.

The above surface treatment of the electrophotographic photosensitivemember was conducted in the following manner. That is, a polishing unit402 in the polishing apparatus body 401 was lifted upward and it wassecured by a clamp 403. Then, the electrophotographic photosensitivemember sample 405 was assembled with a supporting table 404 and theassembly was fixed to the rotary shaft 406. The clamp 403 was thenloosed to lower the polishing unit 402, whereby a polishing roller 407having a fabric disposed on the exterior surface thereof waspress-contacted through the fabric to the surface of theelectrophotographic photosensitive member 405 at a pressure of 10 g/cm²and a nip width of 10 mm by means of a pressure controlling spring 409.An abrasive dispersion 413 containing silicon carbide particles of 8 μmon mean particle size stored in a container 408 was dropwise suppliedthrough an injection pipe 415 onto the polishing roller 407 whilecontrolling the flow rate thereof by means of a valve 414.Simultaneously with the supply of the abrasive dispersion, motors 410and 411 started driving, whereby the surface treatment of theelectrophotographic photosensitive member sample was conducted. In thiscase, the polishing roller 407 was rotated at a speed of 10 mm/minute,and the electrophotographic photosensitive member sample 405 was rotatedat a speed of 300 mm/sec. This surface treatment was conducted for 5minutes. The electrophotographic photosensitive member sample thustreated was washed with ion-exchanged water to remove the abrasivedispersion left on the surface thereof. The resultant was transferredinto a drying vessel, wherein it was dried at 40° C. for an hour tothereby dewater.

The resultant electrophotographic photosensitive member samples wereevaluated in the same manner as in Example 4. As a result, theelectrophotographic photosensitive member samples were found to beexcellent in the electrophotographic characteristics as well as theelectrophotographic photosensitive member samples obtained in Example 4.

In tables 2, 4, 5, 7 and 10, the results of evaluations ofelectrophotographic photosensitive members are provided in which thedefinitions and symbols for photosensitivity evenness; resolution;appearance of interference fringe pattern; appearance of coarseness;white spot appearance; minute line reproducibility; durability;maintenance load and cleaning suitability are as previously recitedherein.

                  TABLE 1                                                         ______________________________________                                        film-forming                                                                              constituent layer                                                 conditions  103        104        105                                         ______________________________________                                        raw material gas                                                              and flow rate                                                                 SiH.sub.4   350    sccm    350  sccm  70   sccm                               He          100    sccm    100  sccm  100  sccm                               B.sub.2 H.sub.6                                                                           1000   ppm     0    ppm   0    ppm                                NO          10     sccm    0    sccm  0    sccm                               CH.sub.4    0      sccm    50   sccm  350  sccm                               SiF.sub.4   0      sccm    1    sccm  0    sccm                               substrate   250°                                                                          C.      250°                                                                        C.    250°                                                                        C.                                 temperature                                                                   inner pressure                                                                            4.0    mTorr   4.0  mTorr 4.0  mTorr                              microwave power                                                                           1000   W       1000 W     1000 W                                  bias voltage                                                                              70     V       70   V     70   V                                  layer thickness                                                                           3      μm   20   μm 0.5  μm                              ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                                                     appearance                                       columnar                     of inter-                                        structure photo-             ference appearnace                               region density                                                                          sensitivity                                                                             reso-    fringe  of                                       (number/cm.sub.2)                                                                       evenness  lution   pattern coarseness                               ______________________________________                                        0.5       x         x        x       ⊚                         1         Δ   Δ  Δ ⊚                         2         Δ   Δ  Δ ⊚                         5         ∘                                                                           ∘                                                                          ∘                                                                         ⊚                         10        ⊚                                                                        ⊚                                                                       ⊚                                                                      ⊚                         100       ⊚                                                                        ⊚                                                                       ⊚                                                                      ⊚                         200       ⊚                                                                        ∘                                                                          ⊚                                                                      ∘                            300       ⊚                                                                        ∘                                                                          ⊚                                                                      ∘                            500       ∘                                                                           ∘                                                                          ⊚                                                                      ∘                            1000      ∘                                                                           Δ  ⊚                                                                      Δ                                  1500      Δ   x        ∘                                                                         x                                        ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        film-forming                                                                              constituent layer                                                 conditions  503        504        505                                         ______________________________________                                        raw material gas                                                              and flow rate                                                                 SiH.sub.4   350    sccm    350  sccm  70   sccm                               He          100    sccm    100  sccm  100  sccm                               B.sub.2 H.sub.6                                                                           1000   ppm     0    ppm   0    ppm                                NO          10     sccm    0    sccm  0    sccm                               CH.sub.4    0      sccm    50   sccm  350  sccm                               SiF.sub.4   0      sccm    0    sccm  0    sccm                               substrate   250°                                                                          C.      250°                                                                        C.    250°                                                                        C.                                 temperature                                                                   inner pressure                                                                            4.0    mTorr   4.0  mTorr 4.0  mTorr                              microwave power                                                                           1000   W       1000 W     1000 W                                  bias voltage                                                                              70     V       70   V     70   V                                  layer thickness                                                                           3      μm   20   μm 0.5  μm                              ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                                                    appearance                                                                    of inter-                                         carbon  photo-              ference appearance                                content sensitivity         fringe  of                                        (atomic %)                                                                            evenness  resolution                                                                              pattern white-spot                                ______________________________________                                        0       Δ   Δ   ∘                                                                         Δ                                   0.5     Δ   Δ   ∘                                                                         Δ                                   1.0     ∘                                                                           ∘                                                                           ∘                                                                         Δ                                   1.5     ∘                                                                           ∘                                                                           ∘                                                                         Δ                                   2.0     ∘                                                                           ∘                                                                           ⊚                                                                      ∘                             2.5     ∘                                                                           ∘                                                                           ⊚                                                                      ∘                             3.0     ⊚                                                                        ⊚                                                                        ⊚                                                                      ⊚                          10      ⊚                                                                        ⊚                                                                        ⊚                                                                      ⊚                          20      ⊚                                                                        ⊚                                                                        ⊚                                                                      ⊚                          23      ∘                                                                           ∘                                                                           ⊚                                                                      ⊚                          25      ∘                                                                           ∘                                                                           ⊚                                                                      ⊚                          28      Δ   Δ   ⊚                                                                      ∘                             30      Δ   Δ   ⊚                                                                      ∘                             33      x         x         ∘                                                                         Δ                                   ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                                       photo-                                                         fluorine content                                                                             sensitivity                                                    (atomic ppm)   evenness  resolution                                           ______________________________________                                        0              Δ   Δ                                              0.5            Δ   Δ                                              1.0            ∘                                                                           Δ                                              1.5            ∘                                                                           Δ                                              2.0            ∘                                                                           ∘                                        2.5            ∘                                                                           ∘                                        3.0            ⊚                                                                        ⊚                                     50             ⊚                                                                        ⊚                                     80             ⊚                                                                        ⊚                                     87             ⊚                                                                        ∘                                        90             ⊚                                                                        ∘                                        93             ∘                                                                           Δ                                              95             ∘                                                                           Δ                                              100            Δ   x                                                    ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        film-forming                                                                              constituent layer                                                 conditions  104(A)     104(B)     105                                         ______________________________________                                        raw material gas                                                              and flow rate                                                                 SiH.sub.4   350    sccm    350  sccm  350  sccm                               He          100    sccm    100  sccm  100  sccm                               B.sub.2 H.sub.6                                                                           1000   ppm     0    ppm   0    ppm                                CH.sub.4    *              *          0    sccm                               SiF.sub.4   *              *          0    sccm                               substrate   250°                                                                          C.      250°                                                                        C.    250°                                                                        C.                                 temperature                                                                   inner pressure                                                                            4.0    mTorr   4.0  mTorr 4.0  mTorr                              microwave power                                                                           1000   W       1000 W     1000 W                                  bias voltage                                                                              70     V       70   V     70   V                                  layer thickness                                                                           1      μm   *          *                                       ______________________________________                                         *disclosed in the description                                            

                                      TABLE 7                                     __________________________________________________________________________              total layer thickness (μm)                                                 20          30          40                                                    photo-                                                                              appearance                                                                          photo-                                                                              appearance                                                                          photo-                                                                              appearance                            thickness of                                                                            sensitivity                                                                         of    sensitivity                                                                         of    sensitivity                                                                         of                                    the layer 104 (μm)                                                                   evenness                                                                            white-spot                                                                          evenness                                                                            white-spot                                                                          evenness                                                                            white-spot                            __________________________________________________________________________    5         ◯                                                                       Δ                                                                             ◯                                                                       Δ                                                                             ◯                                                                       Δ                               6         ◯                                                                       ◯                                                                       ◯                                                                       Δ                                                                             ◯                                                                       Δ                               9         ◯                                                                       ◯                                                                       ◯                                                                       ◯                                                                       ◯                                                                       Δ                               10        ⊚                                                                    ⊚                                                                    ◯                                                                       ◯                                                                       ◯                                                                       Δ                               12        ⊚                                                                    ⊚                                                                    ◯                                                                       ◯                                                                       ◯                                                                       ◯                         15        ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                                                                    ◯                                                                       ◯                         20        ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                      30        --    --    ⊚                                                                    ⊚                                                                    ⊚                                                                    ⊚                      40        --    --    --    --    ⊚                                                                    ⊚                      __________________________________________________________________________

                  TABLE 8                                                         ______________________________________                                        film-forming                                                                              constituent layer                                                 conditions  103        104        105                                         ______________________________________                                        raw material gas                                                              and flow rate                                                                 SiH.sub.4   350    sccm    350  sccm  70   sccm                               He          100    sccm    100  sccm  100  sccm                               B.sub.2 H.sub.6                                                                           1000   ppm     0    ppm   0    ppm                                NO          10     sccm    0    sccm  0    sccm                               CH.sub.4    0      sccm    50   sccm  350  sccm                               SiF.sub.4   0      sccm    1    sccm  0    sccm                               substrate   250°                                                                          C.      260°                                                                        C.    250°                                                                        C.                                 temperature                                                                   inner pressure                                                                            4.0    mTorr   4.0  mTorr 4.0  mTorr                              microwave power                                                                           1000   W       1000 W     1000 W                                  bias voltage                                                                              70     V       70   V     70   V                                  layer thickness                                                                           3      μm   20   μm 0.5  μm                              ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        film-forming  constituent layer                                               conditions    503        504       505                                        ______________________________________                                        raw material gas                                                              and flow rate                                                                 SiH.sub.4     1000   sccm    2000 sccm 1000 sccm                              B.sub.2 H.sub.6                                                                             200    ppm     1.0  ppm  0    ppm                               CH.sub.4      0      sccm    400  sccm 4000 sccm                              substrate temperature                                                                       300°                                                                          C.      300°                                                                        C.   300°                                                                        C.                                inner pressure                                                                              0.5    Torr    0.5  Torr 0.5  Torr                              RF power      500    W       1000 W    500  W                                 layer thickness                                                                             0.5    μm   48   μm                                                                              2.0  μm                             ______________________________________                                    

                  TABLE 10                                                        ______________________________________                                                         Comparative Comparative                                               Example 4                                                                             Example 1   Example 1                                        ______________________________________                                        photo-sensitivity                                                                        ⊚                                                                        x           x                                            evenness                                                                      resolution ⊚                                                                        x           x                                            appearance of                                                                            ⊚                                                                        x           x                                            interference                                                                  fringe pattern                                                                appearance of                                                                            ⊚                                                                        ◯                                                                             ◯                                coarseness                                                                    appearance of                                                                            ⊚                                                                        ◯                                                                             Δ                                      white-spot                                                                    minute line                                                                              ⊚                                                                        Δ     Δ                                      reproductivity                                                                cleaning   ⊚                                                                        ◯                                                                             ◯                                suitability                                                                   durability ⊚                                                                        Δ     Δ                                      maintenance load                                                                         ⊚                                                                        Δ     Δ                                      ______________________________________                                    

                                      TABLE 11                                    __________________________________________________________________________    film-forming                                                                             constituent layer                                                  conditions 103    104    105 (A)                                                                              105 (B)                                       __________________________________________________________________________    raw material gas                                                              and flow rate                                                                 SiH.sub.4  400                                                                              sccm                                                                              300                                                                              sccm                                                                              300                                                                              sccm                                                                              70 sccm                                       He         2000                                                                             sccm                                                                              2000                                                                             sccm                                                                              2000                                                                             sccm                                                                              2000                                                                             sccm                                       B.sub.2 H.sub.6                                                                          1000                                                                             ppm 5  ppm 1  ppm 0  ppm                                        CH.sub.4   200                                                                              sccm                                                                              50 sccm                                                                              0  sccm                                                                              500                                                                              sccm                                       SiF.sub.4  0  sccm                                                                              1  sccm                                                                              0  sccm                                                                              30 sccm                                       substrate temperature                                                                    240°                                                                      C.  270°                                                                      C.  260°                                                                      C.  260°                                                                      C.                                         inner pressure                                                                           10 mTorr                                                                             10 mTorr                                                                             10 mTorr                                                                             10 mTorr                                      microwave power                                                                          1000                                                                             W   1000                                                                             W   1000                                                                             W   1000                                                                             W                                          bias voltage                                                                             100                                                                              V   70 V   70 V   70 V                                          layer thickness                                                                          1  μm                                                                             20 μm                                                                             5  μm                                                                             0.5                                                                              μm                                      __________________________________________________________________________

                  TABLE 12                                                        ______________________________________                                        film-forming                                                                              constituent layer                                                 conditions  104 (A)    104 (B)    105                                         ______________________________________                                        raw material gas                                                              and flow rate                                                                 SiH.sub.4   350    sccm    350  sccm  70   sccm                               He          100    sccm    100  sccm  100  sccm                               B.sub.2 H.sub.6                                                                           1000   ppm     0    ppm   0    ppm                                CH.sub.4    0      sccm    0    sccm  350  sccm                               C.sub.2 H.sub.2                                                                           20     sccm    20   sccm  0    sccm                               SiF.sub.4   1      sccm    1    sccm  0    sccm                               substrate   280°                                                                          C.      300°                                                                        C.    270°                                                                        C.                                 temperature                                                                   inner pressure                                                                            4.0    mTorr   4.0  mTorr 4.0  mTorr                              microwave power                                                                           1000   W       1000 W     1000 W                                  bias voltage                                                                              70     V       70   V     70   V                                  layer thickness                                                                           3      μm   20   μm 0.5  μm                              ______________________________________                                    

We claim:
 1. An electrophotographic photosensitive member comprising asubstrate and a light receiving layer disposed on said substrate, saidlight receiving layer comprising a non-single crystal silicon material amatrix, wherein said light receiving layer contains a plurality ofcolumnar structure regions, each of the columnar structure regions is ofa diameter from 1 μm to 300 μm and each is grown from a nucleuscomprising a crystal material positioned within said light receivinglayer, said plurality of columnar structure regions extending in thedirection of thickness and within said light receiving layer, andcomprising silicon crystals at a density of 5/cm² to 500/cm² formed inthe matrix of said non-single crystal silicon material.
 2. Anelectrophotographic photosensitive member according to claim 1, whereinthe nucleus is set at a position which is distant by 1 μm or more fromthe layer interface of the light receiving layer on the substrate side.3. An electrophotographic photosensitive member according claim 1,wherein the non-single crystal material by which the light receivinglayer is constituted contains carbon atoms in an amount of 2.0 atomic %to 25 atomic % versus the amount of the constituent silicon atoms of thelight receiving layer.
 4. An electrophotographic photosensitive memberaccording to claim 1, wherein the non-single crystal material by whichthe light receiving layer is constituted contains fluorine atoms in anamount of 2.0 atomic ppm to 90 atomic ppm versus the amount of theconstituent silicon atoms of the light receiving layer.
 5. Theelectrophotographic photosensitive member according to claim 1, whereinthe non-single crystal silicon material contains hydrogen atoms.
 6. Aprocess for producing an electrophotographic photosensitive member byintroducing a gaseous silicon-containing raw material into asubstantially enclosed deposition chamber having a discharge space andsupplying a microwave energy into said deposition chamber to generate aplasma in said discharge space thereby forming a light receiving layercomposed of a non-single crystal silicon material as a matrix on asubstrate arranged in said deposition chamber, said process comprisingthe steps of:(i) forming a first partial region of said light receivinglayer, (ii) spacedly depositing a plurality of nucleuses, each of thenucleuses comprising a crystal material and each capable of being anucleus for growing a columnar structure region therefrom on the surfaceof said first partial region in an immobilized state, and (iii) forminga second partial region of said light receiving layer on the surface ofsaid first partial region having said plurality of nucleuses thereonwhile growing columnar structure regions comprising silicon crystalsbased on each of said plurality of nucleuses, each of said columnarstructure regions being of a diameter from 1 μm to 300 μm, therebyforming said light receiving layer containing a plurality of columnarstructure regions comprising silicon crystals at a density of 5/cm² to500/cm² formed in the matrix of said non-single crystal siliconmaterial, said plurality of columnar structure regions comprisingsilicon crystals extending in the direction of layer growth.
 7. Theprocess for producing an electrophotographic photosensitive memberaccording to claim 6, wherein each of the nucleuses is set at a positionwhich is distant by 1 μm or more from the layer interface of the lightreceiving layer on the substrate side.
 8. The process for producing anelectrophotographic photosensitive member according to claim 6, whereinthe non-single crystal material by which the light receiving layer isconstituted contains carbon atoms in an amount of 2.0 atomic % to 25atomic % versus the amount of the constituent silicon atoms of the lightreceiving layer.
 9. The process for producing an electrophotographicphotosensitive member according to claim 6, wherein the non-singlecrystal material by which the light receiving layer is constitutedcontains fluorine atoms in an amount of 2.0 atomic ppm to 90 atomic ppmversus the amount of the constituent silicon atoms of the lightreceiving layer.
 10. The process for producing an electrophotographicphotosensitive member according to claim 6, wherein the nucleuses areintroduced into the reaction chamber while being electrically charged.11. The process for producing an electrophotographic photosensitivemember according to claim 10, wherein the nucleuses are electricallycharged by way of corona charging.
 12. The process for producing anelectrophotographic photosensitive member according to claim 10, whereinthe electrically charged nucleuses are deposited on the surface of thepartial layer region by virtue of an electrical field of 1 V/cm to 100V/cm.
 13. The process for producing an electrophotographicphotosensitive member according to claim 6, wherein the non-singlecrystal silicon material contains hydrogen atoms.